Silvering Mirrors

By D. McClanahan

The art of silvering mirrors has been
held as a valuable trade secret for
many years, but the formulas and
instructions here given makes it
possible for any one with ordinary
care and a little patience to do the
work successfully. I have endeavored
to write these instructions in
order that you may not become
confused.

First you must have a clean
room free from dust, in which
place a steam table made as per
instructions, tho this is not absolutely
necessary, as you can warm
the glass up to 80° to 100° F. by
pouring warm distilled water on
the same. But for those who anticipate
silvering mirrors to any
extent a steam table will be found
necessary. The size of the table
I will leave to you, tho would suggest
to make the table small, say
three by six feet, until you become
more proficient in the art.

Make a box three by six feet,
open at the top; for legs use two
by four timber. Bolt the legs to
the box frame at A, Fig. 1. Next
take a piece of iron three feet long,
two inches wide and one-quarter
inch thick, placing it across each end
so the steam pipes may rest upon it,
B, Figs. 1, 2, 3. This is to prevent
the boards on the bottom of the
table from burning. Place one-inch
pipes in the table as in illustration,
Fig. 3-C ; on top of the pipes is
placed an iron top, three by six
feet and one-quarter inch thick.

(Note.—It is best to go to a foundry
and secure your iron plate
first and build your frame work
to fit the plate, for sometimes it is
hard to get iron plate the exact
size you want it.)

This iron top
must rest flush with the side boards
D, Fig. 1. This is done by making
a quarter-inch groove on all four sides of
the table. Now cover the iron top with
unbleached muslin, stretch and tack to the
side boards.

Make a wooden gutter all around the
table, E, Figs. 1 and 3, about three inches
wide, and at F, Figs. 1 and 3, make a hole
and place a spout in it. The table is connected
to a steam boiler or hot water
heater, using suitable valves V, V, as
shown, to control the steam inlet and outlet
pipes.

Do not attempt to handle a very large
glass at first. One a foot square will be
large enough to start with. Obtain a good
grade of plate glass free from scratches.

Next get some polishing rouge, which
comes in powdered form. Place in a bag
made of two or three thicknesses of cotton
flannel, sew bag up, place in water to soak,
then take the rouge bag and rub over the
glass while the rouge is still wet ; then rub
well with your polisher, Fig. 4. This is a
block of wood measuring six by three
inches, having two handles for holders, B,
Fig. 4, with a thick felt rubber attached at
the bottom, C, Fig. 4. Keep the felt wet
and proceed to polish the glass all over the
surface that is to be silvered, being careful
to. polish right to the edges. When the
rouge has dried, wipe it off. When thru
polishing avoid touching the polished side
with your fingers, as this would leave a
grease spot and the silver would not adhere
to the glass where you touched it. Put
your hands under the glass and place it on
your washing table and clean as follows:

Washing Solution

Take one- fourth ounce of muriate of tin
crystals to ten ounces of water, and from
this solution take one ounce and add it to
one pint of water. This one pint of water
should look a very light blue in color. Now
pour on the glass and rub off with a felt
block like Fig. 4, but minus the handles.

Be sure to rub only one way, then pour
on a lot of hydrant water, rubbing it off
with another felt block. Place your hands under
the glass and put it on the steam
table, which has been previously warmed
up to 90° to 100° F. Keep the side to be
silvered up. Now level the glass by placing
wooden wedges, see Fig. 5, under the edges.
Pour warm distilled water on the glass in
the same manner as the silver solution will
later be poured on.

By pouring distilled water on glass and
placing wedges as may be needed you can
level the glass until you have an even layer
of water standing all over it. Should the
distilled water be slow in covering the
edges, take your glass rod and draw the
water by scraping along the edges. When
you get the glass level, raise one side
slightly and let all the distilled water run
off, laying the glass back in place gently,
being very careful not to displace the
wedges, thereby making the glass unlevel.

How to Silver

Pour your silver solutions No. 1 and
No. 2 into a glass or stone pitcher, using
the exact proportions as given in the formula
below, stirring the solutions with a
glass rod or by pouring from one pitcher
to another. Now pour into the center of
the glass without stopping as the precipitation
commence-- at once, or as soon as the
solutions are mixed.

Let the solution flow out until the entire
surface is covered, allowing it to stand
thirty or forty minutes to precipitate,
then tip the glass on one corner,
allowing all the solution that
will to run off.

Next clean by pouring on the
hike-warm distilled water, place the
glass back on the wooden wedges
for a few minutes to dry. When
dry coat the side that is silvered
with a mixture of orange shellac—
two ounces; wood alcohol, one pint;
turpentine six ounces. Use a camel's
hair brush to smooth it out—after
this is dry, paint over with a camel's
hair brush and some asphaltmn
varnish.

The Boiled or Cold Process

Solution No. 1—Take 150 grains
of nitrate of silver. AgNO3, crystallized
salt C. P., dissolve in 1
pint of distilled water and to this
add with a glass eye-dropper concentrated
or 26% ammonia, one
drop at a time, until it turns dark
keep on dropping the ammonia until
it turns light again—then put in
130 grains more of silver, AgNO3
and let it dissolve-now pour this
into 3 pints of distilled water first
measured out. Have a ribbed funnel
and in the neck of same press
a little absorbent cotton before you
put in the filtering paper—now put
in the ribbed funnel two sheets of
filtering paper and filter the solution—
it is then ready for use.

Solution No. 2—Take 96 grains
of crystallized Rochelle salts, place
in one-half gallon of warm distilled
water, using a porcelain lined vessel.
Let this come to a strong boil
for about two minutes, then add
96 grains more of AgNO3 and let
for six minutes longer. As soon
solution is cool, it is best to pour
it from the porcelain vessel in which it
was boiled into some glass vessel, as the
vessel that you boiled this solution in will
be quite dirty. Filter this solution the same
as you did solution No. 1—into a separate
pitcher—when ready to silver mix the two
and flow on the glass. Let stand for 15 or
20 minutes.

The Caustic Potash Process

Solution No. 1—Take 3 pints of distilled
water—measure from this amount 4 ounces
and add to the four ounces of distilled
water 240 grains of AgNO3-let dissolve
-
then take concentrated or 26% ammonia,
3 1/2 drachms and add it drop by drop until
the sediment is nearly redissolved then add
the balance of the water—let this stand 12
hours and filter.

Solution No. 2—Take 48 ounces of distilled
water and divide into 3 parts and
add to the first part 180 grains of AgNO3.
add to the second part 20 grains of caustic
potash—add to the third part 1 3/4 ounces of
crystal Rochelle salt C. P.
Mix all three—shake well and let stand
for 12 hours and filter. To use, mix 4
parts of Solution No. 1 and 1 part of Solution
No. 2-stir with a glass rod and
pour on glass at once—allowing 35 to 40
minutes to precipitate.

The French or Tartaric Acid Process

Solution No. 1—Take 8 ounces of
AgNO3, dissolve in 8 ounces of
concentrated or 26% ammonia—when the silver
has dissolved add 1/2 pint of distilled water
and let it stand 24 hours—filter and it is
then ready for use.

Solution No. 2—Dissolve 8 ounces of
tartaric acid in one quart of distilled water,
let it stand for 24 hours—the older this
solution gets the better. Reduce this to
10% by using an acid hydrometer—if it
should be stronger than 10% add distilled
water until it becomes so. Filter before
using.

To silver, take 4 ounces of Solution No.
1, put it into 1 quart of distilled water.
Take 4 ounces of Solution No. 2, put it
into 1 quart of distilled water—next mix
Solutions No. 1 and No. 2 by pouring from
one pitcher to another—then flow the solution
on the glass, allowing it to remain for
one hour.

Metallic Mirror Process

Make a liquid preparation by melting into
a porcelain vessel 1 dram of lead, 1 dram of
tin, 1 dram of C. P. Bismuth. When these
are melted together add 10 drams of mercury
before the mass has cooled. The
mercury will cool it sufficiently for use.
Lay the glass flat with the clean side up
and pour the metallic liquid over it, completely
covering. Raise the glass almost
perpendicular, letting the amalgam drain
off. When the coating has become hard
and dry, coat with drop black ground in
Japan, and then thin with turpentine.